Method of forming a coated abrasive wheel



M y 1963 J. H. HOHENBER'GER 3,382,057

METHOD OF FORMING A COATED ABRASIVE WHEEL Filed ga '27. 1965 INVENTOR JOHN H. HOHEN 552cm? ATTORNEY United States Patent 3,382,057 METHOD OF FORMING A COATED ABRASIVE WHEEL John H. Hohenberger, Williamstown, Mass., assignor to Norton Company, Troy, N.Y., a corporation of Massachusetts Filed May 27, 1965, Ser. No. 459,413 4 Claims. (Cl. 51-293) ABSTRACT OF THE DISCLOSURE A plurality of coated abrasive flaps having at least one hole in the base of each is strung on an elastic member while the elastic member is under tension. The ends of the elastic member are joined to form an annulus and the tension is then released causing the elastic member to contract in length and expand in diameter to give a closer compaction of the flaps than can be accomplished with a non-stretchable stringer.

The present invention relates in general to coated abrasive products and more specifically to such products in the form of cylindrical wheels commonly referred to as flap wheels and to an improved method of assembling such flap wheels.

Coated abrasive wheels composed of a plurality of separate segments or flaps radially disposed about a central core and fastened so as to provide a wheel structure have long been known to the art. Typical structures of this type are illustrated in US. Letters Patent No. 2,651,894 to G. O. Leggett and US. Letters Patent No. 2,978,845 to E. S. Haven et al.

The actual assembly of these flaps of coated abrasive material into a wheel has been a time-consuming and largely hand operation. In an effort to facilitate such assembly, the flaps have been assembled into packs and adhered at one end to a flexible strip which is brought around into an annular shape to form the wheel. Likewise the flaps have been strung on wires passing through holes in the base of each flap and the use of elastic restraining means about packs of the flaps have been tried -all with varying degrees of success.

It is therefore an object of the present invention to provide an improved method of assembling a coated abrasive flap wheel.

A further object of the invention is the provision of a method which permits tighter packing of flaps in a flap wheel with a corresponding increase in the density of the finished wheel.

Additional objects, if not specifically set forth herein, will be readily apparent to one skilled in the art from the following detailed description of the invention.

In the drawings:

FIGURE 1 is a schematic illustration of the first phase of the method of the present invention.

FIGURE 2 is a schematic illustration of the second phase of the method of this invention.

FIGURE 3 is a partial perspective view showing assembly of a flap wheel in accordance with the invention.

FIGURE 4 is a schematic illustration of one means for fastening the ends of the flexible retainer used in the present method.

Generally, the present invention is based on two concepts:

(1) By forming an assembly of flaps about a larger center or greater diameter core than will be in the finished wheel, a greater number of flaps may be put into the assembly; and

(2) By utilizing a stretchable, elastic retainer or stringer 3,382,057 Patented May 7, 1968 which reduces in diameter when placed under tension and increases in diameter when tension is at least partially relaxed, friction between such retainer and the flaps through which it passes will, upon relaxing of tension on the retainer, cause the flaps to pack very tightly together.

More specifically, and referring now to the drawings, FIGURES 1 and 2 show schematically how the method of the present invention operates. Reference numeral 10 indicates a die-cut coated abrasive flap, generally rectangular in shape, with a pair of opposed notches or grooves 111 extending inwardly from the lateral edges near one end of the flap. A hole 12 is provided in the end of each flap 10 at the same end thereof as the notches 11. The flap 10, described and illustrated as above, is conventional in shape and formation. Extending through the hole 12 in each flap is a stretchable, elastic member 13. As shown in FIGURE 1, this elastic member 13 is under tension and as such has a diameter slightly smaller than that of the hole 12 through which it passes. A plurality of fiaps.10, each with an abrasive face 14, are shown strung onmember 13. These flaps are assembled. by passing member 13 through hole 12 of each and then sliding the flaps into a reasonably packed relationship as shown in FIG- URE 1. FIGURE 2 illustrates what happens when tension is released on member 13. The stretchable member 13 will contract lengthwise with an increase in diameter until it snugly fits the inner diameter of hole 12 in each of the flaps 10. Frictional engagement between the flaps 10 and member 13 during this contracting and expanding operation causes the flaps to be drawn in tightly against one another in extremely tight-packed relationship. While one hole and one retainer is illustrated and described above, when using wide flaps it may be desirable to use more than one retainer and correspondingly more than one hole in each flap.

In actual practice, the flaps 10 are assembled as shown in FIGURE 3 with the flaps being strung on stretchable member 13 disposed under tension about a mandrel or core 15 which is of greater diameter than the intended final diameter of the wheel. After the flaps have been packed tightly on the member 13 (by hand or machine) the ends 16-46 of member 13 are fastened to each other as shown in FIGURE 4. This may be accomplished in a variety of ways, e.g. by having a fastening device incorporated in each end, by a twist formed in the ends or, as illustrated, by simply inserting a pin 17 or other rigid fastener through the two ends 16-16. Mandrel 15 is then removed from inside of the annular ring of flaps so formed and the assembly will snap back to the intended diameter as the length of member 13 contracts and the flaps 10 are pulled into extremely close relationship by the friction between the material of the flap around the holes 12 of each flap and the expanded diameter of member 13. Annular retaining rings of metal, plastic or the like are then placed in the grooves formed by notches 11 in the flaps and secured in place by an adhesive if desired. The inner end of the flaps may be impregnated with an adhesive during assembly or after if desired in known fashion. Adhesives such as those disclosed in US. Letters Patent Nos. 2,843,469 and 2,842,902 to Miller et al. may be employed to assist in retaining the flaps in a rigidified structure if so desired.

The stretchable member employed in the method of the present invention may be made as a tube of solid strand of any suitable elastic material such as natural or synthetic rubber or the like, or may even be formed of metal, in the form of a spring or coiled tube. The only requirements are that the material is sufliciently strong to permit stretching to the desired degree, that upon release of tension the material will contract to approximately its original length and that upon stretching it will decrease in diameter relatively uniformly and will gain back such diameter decrease uniformly upon release or partial release of tension. The preferred material is a hollow rubber tube, approximately in diameter, having a stretch at break of about 270% and a breaking tensile of about 70 pounds.

As an example of the method of the present invention a flap wheel was prepared from a conventional resinbonded coated abrasive material (Metalite cloth, Type 101, grit 80 material made by Behr-Manning Division of Norton Company). The flaps were die-cut from this material to a rectangular dimension of 1" x 2Vs".The opposed notches in each side were from the inner end of the flaps and extended into the flap A". The hole for use in stringing the flaps was of 7 diameter. The stretchable member, formed of the preferred rubber described above was a hollow tube of 7 diameter in its unstretched state and since the desired wheel was to have an internal diameter of 2%" at the notches and 1%" actual hub internal diameter, the stretchable member was 7 in length. A mounting mandrel of 2'' CD. was used and the stretchable member was fastened at one end to such mandrel. The stretchable member was then placed under tension and stretched to give it a reduced diameter of A". Two-hundred and twenty flaps were then assembled by stringing the same on the stretched member. The ends of the member were then fastened to each other and the unit slipped off the mandrel whereupon it immediately snapped back to form a wheel of 1%" inside hub or core diameter. This wheel was self-sustaining without the side flanges. However, in the interest of strength and safety, metal side flanges with laterally extending rings (such as illustrated in U.S. Letters Patent No. 2,842,902 to Miller et al.) were inserted in the side grooves formed by the opposed notches in the flaps and held in place by an epoxy resin adhesive previously applied inside said notches. As a comparison with the density of the wheel prepared as described above, an exactly similar wheel of the same finished diameter was prepared from the same flaps but without utilizing the present method. The maximum number of flaps which could be introduced into the wheel was 185 whereas, in the wheel prepared by this invention, 220 flaps were able to be incorporated in the assembly.

Obviously, many variations may be made without departing from the spirit and scope of the invention as disclosed herein and, therefore, only such limitations should be imposed as are contained in the appended claims.

I claim:

1. A method of forming an abrasive wheel having a plurality of radially extending coated abrasive flaps which comprises:

forming a plurality of coated abrasive flaps each with at least one hole adjacent the inner end thereof;

providing at least one elastic member which, when under tension, is of lesser diameter than said hole 2 in said flaps; assembling said flaps into an annulus by passing said elastic member through at least one of said holes in each of said flaps while said member is under tension;

fastening the ends of said elastic member together; and

then releasing tension on said elastic member to permit it to contract in length and to expand in diameter to frictionally engage and compress together the inner ends of said flaps. 2. A method of forming an abrasive wheel having a plurality of coated abrasive flaps extending radially outward from a central open core which comprises:

forming a plurality of coated abrasive flaps each with a hole adjacent the inner end thereof;

providing an elastic, stretchable member which, when under tension, is of lesser diameter than said hole in said flaps and a mandrel which is of greater diameter than the intended central open core of said wheel;

assembling said flaps into an annulus in contact with and about said mandrel by passing said elastic, stretchable member through said hole in said flaps while said member is under tension;

fastening the ends of said elastic, stretchable member one to the other While said member is still under tension; and

removing said mandrel from contact with said annulus of flaps to release tension on said elastic, stretchable member and to permit it to contract in length and expand in diameter to frictionally compress the inner ends of said flaps to form a central core opening of lesser diameter than said mandrel.

3. A method as in claim 2 where adhesive is applied to the inner ends of said flaps to adhere said flaps one to the next.

4. A method as in claim 2 wherein opposed notches are provided in said flaps, said notches forming annular grooves about the finished wheel, and wherein reinforcing flanges are disposed within said grooves.

References Cited UNITED STATES PATENTS 2,164,800 6/1939 Davis 51--337 2,843,469 7/1958 Miller et al 51-293 3,241,267 3/1966 Block et al. 51293 3,294,502 12/1966 Schatfner 51-293 D. J. ARNOLD, Primary Examiner. 

